With continuous expansion and upgrade of a network, to control costs and power consumption, optical modules are inevitably developing toward miniaturization. To achieve this objective, sizes of optical components and circuits in the optical modules need to be reduced. However, a method for reducing the sizes of the optical components is mainly to replace conventional discrete optical components with integrated waveguide components having a high refractive index difference. In the prior art, common waveguide materials having a high refractive index difference include silicon, silicon nitride, polymer (for example, SU8), and III-V compound semiconductor materials such as InP. Optical components made of these materials have a very strong polarization correlation, that is, transverse electric (Transverse Electric, TE) mode polarized light and transverse magnetic (Transverse Magnetic, TM) mode polarized light have different operating wavelengths. However, some network applications require that optical components in a receiver should have a polarization-insensitive feature, that is, require that operating wavelengths of TE polarized light and TM polarized light should be the same.
FIG. 1 shows a schematic structural diagram of a micro-ring resonator provided by the prior art. As shown in FIG. 1, input light in an unknown polarization state is split by a polarization splitter (Polarization Splitter, PS) into TE light and TM light, which are respectively processed by using micro-ring resonators having a same operating wavelength and then undergo polarization combination by using a polarization combiner (Polarization Combiner, PC). It is required that operating wavelengths of the two micro-rings should be the same, and that included waveguides should have a strong polarization correlation. Radii of the micro-rings are different, and are R and R′ respectively. In order that the two micro-rings are not coupled to each other, it is assumed that a minimum distance between the micro-rings is Gap. In the used solution in FIG. 1, a distance between components is limited by a resonator radius, and is at least 2*R+2*R′+Gap, and cannot be further reduced. A disadvantage of the solution in FIG. 1 is that two sets of components need to be used, and that control complexity and power consumption are both doubled. Secondly, in the used solution, a difference between operating wavelengths of TE polarized light and TM polarized light is limited by a current process level and a minimum distance between micro-rings, and requirements of dense wavelength multiplexing (Dense Wavelength Division Multiplexing, DWDM) applications cannot be satisfied.